MECHANICAL ENGINEERING INTERVIEW TECHNICAL QUESTIONS
Q21. What are killed steels and what for these are used?
Ans. Killed steels are deoxidised in the ladle with silicon and aluminium. On solidification no gas evolution occurs in these steels because they are free from oxygen.
Q22. What are the major effects of alloying elements?
Ans. (1) To alter the transformation temperatures and times.
(2) To modify the room temperature and elevated temperature strengths of given structures by (a) stiffening the crystals and (b) introducing complex precipitates which tend to harden the steel.
(3) To modify the type of oxide film formed on the surface of the steel and thereby affect its corrosion resistance.
Q23. What is the role of silicon as alloying element in steels ?
Ans. Silicon contributes greatly to the production of sound steel because of its deoxidizing and degasifying
properties. When added in amounts upto 2.5%, the ultimate strength of the steel is increased without loss in ductility. Silicon in excess of 2.5% causes brittleness, and amounts higher than 5% make the steel non-malleable. Resistance to oxidation and surface stability of steel are increased by the addition of silicon. These desirable effects partially compensate for the tendency of silicon to lower the creep properties of steel. Silicon increases the electrical resistivity of steel and decreases hysteresis losses.
Q24. Define buckling factor.
Ans. It is the ratio of the equivalent length of column to the minimum radius of gyration.
Q25. What is coaxing ?
Ans. It is the process of improving fatigue properties by first under-stressing and then increasing· the stress in small increments.
Q26. What is a ceramic ?
Ans. It may be defined as a solid formed by the combination of metallic and nonmatallic elements. Some examples are Zirconia (ZrO2), Tungsten carbide (WC), Boron nitride (BN).
Q27. Explain difference between modulus of resilience and modulus of rigidity ?
Ans. Modulus of resilience is the maximum strain energy stored in a material per unit volume and modulus of
rigidity is the ratio of shearing stress to the shearing strain within the elastic limit.
Q28. Describe transfer machines in brief.
Ans. It is an automatic machine in which workpiece alongwith fixture is transferred from one station to other automatically and several operation on workpiece are performed at each station.
Q29. The graphite in grey irons exists in the form of flakes which act as stress-raisers under tensile loading and consequently grey irons have relatively low tensile strength and ductility. Still grey iron is extensively used in engineering. Why ?
Ans. Grey iron is extensively used in engineering because of following characteristics :
(b) Low melting point and high fluidity making it suit- able for castings of intricate shape.
(c) Relatively good erosion and corrosion resistance.
(d) High damping capacity, with respect to vibration.
1) Relatively good mechanical properties under com-pressive loading.
Q30. What is the different between brass and bronze’?
Ans. Brass is an alloy of copper with zinc; and bronze is alloy of copper with tin.
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Mechanical Engg. Interview Questions – Section-2
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Mechanical Engg. Interview Questions – Section-5
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Mechanical Engg. Interview Questions – Section-7
Mechanical Engg. Interview Questions – Section-8